Phase shifters are two-port network devices that provide a controllable phase shift (i.e., a change the transmission phase angle) of a radio frequency (RF) signal in response to control signal (e.g., a DC bias voltage). Conventional phase shifters can be generally classified as ferrite (ferroelectric) phase shifters, integrated circuit (IC) phase shifters, and microelectromechanical system (MEMS) phase shifters. Ferrite phase shifters are known for low insertion loss and their ability to handle significantly higher powers than IC and MEMS phase shifters, but are complex in nature and have a high fabrication cost. IC phase shifters (aka, microwave integrated circuit MMIC) phase shifters) use PIN diodes or FET devices, and are less expensive and smaller in size than ferrite phase shifters, but their uses are limited because of high insertion loss. MEMS phase shifters use MEMS bridges and thin-film ferroelectric materials to overcome the limitations of ferrite and IC phase shifters, but still remain relatively bulky, expensive and power hungry.
While the applications of phase shifters are numerous, perhaps the most important application is within a phased array antenna system (a.k.a., phased array or electrically steerable array), in which the phase of a large number of radiating elements are controlled such that the combined electromagnetic wave is reinforced in a desired direction and suppressed in undesired directions, thereby generating a “beam” of RF energy that is emitted at the desired angle from the array. By varying the relative phases of the respective signals feeding the antennas, the emitted beam can be caused to scan or “sweep” an area or region into which the beam is directed. Such scan beams are utilized, for example, in phased array radar systems and other object-detection systems to sweep areas of interest (target fields), where beam energy portions that are reflected (scattered) from an object located in the target field are detected and analyzed to determine the object's position.
Because a large number of phase shifters are typically needed to implement a phased array-based system (e.g., an object-detection system such as radar), the use of conventional phase shifters presents several problems in such phased array-based systems. First, the high cost of conventional phase shifters makes phased array-based systems impractical (i.e., too expensive) for many applications that might otherwise find a phased array useful—it has been estimated that almost half of the cost of a phased array is due to the cost of phase shifters. Second, high power consumption of conventional phase shifters precludes mounting phased arrays on many portable devices and small vehicles that rely on battery power or have otherwise limited power sources, thus limiting the types of devices and vehicles that could power a phased array for a practical amount of time. Third, phased arrays that implement conventional phase shifters are typically highly complex due to the complex integration of many expensive solid-state, MEMS or ferrite-based phase shifters, control lines, together with power distribution networks, as well as the complexity of the phase shifters. Moreover, phased array systems implementing conventional phase shifters are typically very heavy, which is due in large part to the combined weight of the conventional phase shifters), which limits the types of applications in which phased arrays may be used. For example, although commercial airliners and medium sized aircraft have sufficient power to lift a heavy radar system, smaller aircraft, automobiles and drones typically do not.
What is needed is an object-detection system that avoids the weight (bulk), expense, complexity and power consumption of conventional phased array-based object-detection systems. What are also needed are guidance and collision avoidance systems utilizing such object-detection systems.